Restoration of degraded low-lying grasslands: indicators of the environmental potential of botanical nature quality

Abstract To select grassland sites for successful botanical restoration, it is essential that there is both a biological (a species pool) and an environmental potential (suitable conditions for the species to establish). Our aim was to identify indicators of the environmental potential of botanical quality measured independently of the species composition of the vegetation. Data were collected on numerous sward, soil, and grassland management variables at 20 Danish low-lying grasslands managed under different intensities. Top soil from each site was bioassayed with oat ( Avena sativa L.) as a phytometer. Correlation analyses were used to examine relationships among variables and groups of variables. Indicators independent of species composition of the vegetation related to high or low botanical nature quality were identified. Indicators for high potential nature quality were the K/P ratio in the sward and K concentration in bioassay plants. Indicators for low potential nature quality were dry matter (DM) production, feed units and P -concentration of the sward; dry weight, shoot number and leaf length in bioassay; potential N mineralisation rate and amount of mineral N in the soil in spring. We concluded that a combination of indicators was preferable to only one indicator, as botanical nature quality is influenced in a multi-factorial way.